Hydrocarbon conversion process

ABSTRACT

Method for producing hydrogen and a hydroprocessed product from a hydrocarbonaceous feedstock by subjecting it to a catalytic hydrocracking treatment using hydrogen which has been at least partly produced from hydrocracked feedstock and subjecting at least pan of the hydrocracked feedstock, after having subjected it to a separation treatment in the event that hydroprocessed product is to be recovered, to a treatment to produce hydrogen in a single operation which hydrogen is at least partly recovered as product.

The present invention relates to a process for convertinghydrocarbonaceous feedstocks in a flexible manner.

For many years, refiners have been, and to some extent still are,focusing on maximising the size of the capacity as far as possible or onoptimising the infrastructure of existing refineries in order tominimise costs or, even better, to find the most pragmatic solution forboth maximising throughput and optimising infrastructure. In thisapproach, and even when designing grass-roots refineries, the emphasisis on large refineries as the huge costs involved can only be justifiedby the processing of large amounts of feedstocks, especially since thepresent day markets are international and product made in one locationcan be sold in other locations. Such refineries, sometimes referred toas export-refineries, have proven their existence over the years.

In the context of existing refineries it is understandable because offixed logistics that adaptations are designed in such a way that theyfit with the current infrastructure which means that whilst certainadaptations may possibly be optimal for a certain part of the refinery,they most likely are not for another part, or even all other parts ofthe refinery.

In order to curb the costs of refineries one can think of downsizing thescale of the operations but it is easy to understand that in downsizingthe scale of a refinery, the advantages gained because of the increasein size, and its complementary optimisation of the intrinsicinfrastructure are lost, if not completely than at least to a largeextent.

Moreover, fixed operations like those performed in huge refineries donot have much flexibility and one can not cope easily with changes inthe market place, in particular when such changes would be radical,rather frequent and not easy to predict.

An example of a refinery scheme which has been designed to become moresimple in that it could be built on a compact plot plan and at possiblylow capital investment costs has been described in European publishedpatent application EP-A-635555. In essence, the refinery scheme asdisclosed in EP-A-635555 is directed at operating a single hydrotreatingunit followed by a distillation into a number of fractions.

The difference between the refinery scheme as proposed in EP-A-635555and the prior art referred to in said document is said to be that inconventional refining crude oil is separated into several fractionswhich are then (hydro)treated individually. The results described whenusing a feedstock containing C5-360° C. material (the total of the fourfractions normally obtained when the feedstock is firstly subjected todistillation) give the impression that a refinery can be simplified to agreat extent without reducing the hydrotreating effect obtained in theprior art. It is clear, however, that when the fraction containing C4and lower hydrocarbons (the C4-fraction), also forming part of the crudeoil taken in but not forming part of the hydrotreating process of theC5-360° C. material, is used additionally in the single hydrotreatingunit, the results are less encouraging. It is further stated inEP-A-635555 that part of one of the products obtained after distillationcan be sent to a catalytic reformer in order to produce hydrogen whichcan be used in the single hydrotreating step.

In U.S. Pat. No. 3,463,611 a process has been described which is aimedat recovering sulphur from sulphur-containing feed streams by a rathercomplex line-up designed at concentrating hydrogen sulphide in asufficiently high concentration in a recycle stream of which a purge gasstream is fed to a partial oxidation zone after which hydrogen sulphideand carbon dioxide removed from that zone are led to a Claus process forthe manufacture of sulphur. The process as described in U.S. Pat. No.3,463,611 is in essence a hydrogen consuming process which may needadditional make up hydrogen which can be fed into the hydrogen line tothe hydroconversion unit.

In U.S. Pat. No. 3,224,958 a process has been described in which ahydrocarbon feed is separated into a light and a heavy fraction whichare separately subjected to a hydroconversion step followed by combinedworking up of the converted feedstocks comprising a catalytichydrogenation unit, a gas generator and a shift reactor in order toproduce recycle hydrogen of passable quality. Some hydrogen of lowquality is removed as a purge stream prior to the gas generator andshift conversion stages. In essence, the process as described in U.S.Pat. No. 3,224,958 is directed at the production of hydrocarbons ratherthan hydrogen.

In U.S. Pat. No. 3,189,538 a process has been described in whichhydrogen is produced not only from a converted feedstock but also from acracking/regeneration system tailored to produce hydrogen from anauxiliary charge whilst integrating parts of the cracker/regeneratoroverhead with the hydrogen supply to the hydrogen consuming process. Inessence, the process as described in U.S. Pat. No. 3,189,538 isinflexible in that it requires two not integrated hydrogen productionunits, one of which being a fluidized cracking unit which is veryexpensive and not normally used as a hydrogen production facility.Moreover, in order to operate such process no less than three differenthydrocarbon charges have to be used to supply the main conversionprocesses.

It has now been found that flexibility can be improved by furtherprocess integration to the extent that part of the product obtained in ahydrocracking operation should be used as feedstock for producinghydrogen which is used in the hydrocracking operation to produce thedesired refinery products. The hydrocracking operation should be carriedout in such a way that, depending on the product slate envisaged, afraction is produced which can be used optimally in the production ofhydrogen. This means that the process according to the present inventionachieves the combined goals of reconstituting the feedstock by thetreatment in the hydrocracker whilst at the same time producing orincreasing the amount of the fraction which is elected to serve in totoor in part as feedstock for the hydrogen production facility to be usedin the hydrocracking operation.

The present invention therefore relates to a process for producinghydrogen and a hydroprocessed product from a hydrocarbonaceous feedstockby subjecting it to a catalytic hydrocracking treatment using hydrogenwhich has been at least partly produced from hydrocracked feedstock andsubjecting at least part of the hydrocracked feedstock, after havingsubjected it to a separation treatment in the event that hydroprocessedproduct is to be recovered, to a treatment to produce hydrogen in asingle operation which hydrogen is at least partly recovered as product,characterised in that the amount of hydrogen produced by the processexceeds the amount of hydrogen needed in the process.

The process according to the present invention comprises therefore inessence a hydrocracking operation, optionally a separation operation anda hydrogen production operation provided with the appropriate feedinlet, product outlet(s) and hydrogen transfer line(s).

The process according to the present invention can be carried out in anumber of ways, depending on the nature of the feedstock, the severityof the intended hydrocracking operation and the type and amount of thespecific hydrocracked feedstock fraction to be used as feedstock for thehydrogen producing facility.

Hydrocarbonaceous feedstocks which can be suitably applied in theprocess according to the present invention are those ranging from havingan initial boiling point of about ambient to those having a finalboiling point of about 650° C., measured under standard conditions oftemperature and pressure (20° C. and 1 atmosphere). It will be clearthat feedstocks which can be applied in the method according to thepresent invention do not need to have a boiling range profileencompassing the total range disclosed hereinabove. Feedstocks having aboiling point range such that their 90% boiling point (i.e. thetemperature at ‘which ’90% of the feedstock would have been distilledoff in a distillation process) lies in the range between 400 and 600° C.can be advantageously applied. Preference is given to feedstocks havinga 90% boiling point in the range between 450 and 600° C. Good resultscan be obtained with feedstocks having a 90% boiling point in the rangefrom 475 to 550° C.

Examples of feedstocks which can be suitably applied are naphtha,kerosene and various types of gas oils such as atmospheric gas oil andvacuum gas oil. Also cycle oils can be suitably applied. Not onlyfeedstocks from mineral origin but also from synthetic origin can beapplied. Synthetic or semi-synthetic feedstocks are preferred from a lowsulphur and/or nitrogen point of view as such feedstocks reduce thenecessity of having sulphur and/or nitrogen removing processes formingpart of product upgrading. Hydrocarbonaceous materials formed fromsyngas via the so-called Fischer-Tropsch process form a very usefulfeedstock for the process according to the present invention as suchfeedstocks would obviate the need for sulphur and/or nitrogen treatmentand removal facilities.

It is possible that the hydrocarbonaceous feedstocks to be applied inthe process according to the present invention contain also materialsboiling below ambient temperature. Such materials may be present in thefeedstock to be applied or can be added to such feedstock. Reference ismade to the presence of lower hydrocarbons or hydrocarbon fractions suchas liquefied petroleum gas.

It is advantageous to use a feedstock which contains between 5 and 40%by weight of material having a boiling point range which is higher thanthe boiling point range of the hydroprocessed product.

Feedstocks containing sulphur containing materials can also beprocessed. Normally, the amount of sulphur will not exceed 5% by weight,and preferably will not exceed 3% by weight. Preference is given tofeedstocks containing even lower amounts of sulphur, or no sulphur atall.

It will be clear to those skilled in the art that extraneous hydrogenwill have to be introduced in the context of the start-up of the processaccording to the present invention. Part or all of the hydrogen to beconsumed during the hydrocracking step of the process according to thepresent invention will be generated in the hydrogen manufacturing unitforming part of the line-up.

The catalytic hydrocracking treatment in according with the presentinvention can be suitably carried out at temperatures in the rangebetween 200 and 550 DC, preferably between 250 and 450° C. Pressures upto 400 bar can be suitably applied, preference is given to pressures inthe range between 10 and 200 atmospheres.

In the process according to the present invention at least part of thehydrogen to be used in the hydrocracking treatment will be generatedfrom hydrocracked feedstock. Therefore, catalyst are preferably usedwhich are capable of converting not only that part of the feedstockwhich delivers the hydroprocessed product but also of converting otherparts of the feedstock to such an extent that the remaining hydrocrackedfeedstock is a good source for hydrogen production. In other words,preference is given to catalysts which also produce large amounts oflower boiling materials (besides the hydrocracked product).

Examples of catalysts which can be used in the hydrocracking treatmentin accordance with the process in accordance with the present inventionare zeolitic catalysts having a tendency to overcrack hydrocarbon-aceousmaterial from a conventional point of view (in which as far as possibleonly those fractions of the feedstock are cracked which deliver thedesired hydrocrackate whilst preserving as much as possible of theinitial feedstock, or at least to the extent that liquid material willremain and therefore minimising the production of gaseous material). Inthe process in accordance with the present invention, it is advantageousto apply hydrocracking catalysts which are capable of producing besides,the desired product(s) also a fair amount of lower boiling materials,which from a conventional hydrocracking point of view is not preferredat all. Examples of such catalysts can be based on zeolite beta, zeoliteY, ZSM-5, erionite and chabazite. It will be clear to those skilled inthe art which specific zeolite material and which specific metal(s)having hydrocracking capabilities can be used, taking into account thatpreference is given to catalysts giving rather high yields on relativelylights products as such products reduce the severity of that part of theprocess which is directed at the production of hydrogen. As an examplesuitable catalysts comprise zeolite beta containing one or more of GroupVI and/or one or more of Group VIII metals. Examples of Group VI metalscomprise Mo and W. Examples of Group VIII metals comprise Ni, Co, Pt andPd. Suitable catalysts contain between 2 and 40% by weight of Group VImetals and/or between 0.1. and 10% by weight of Group VIII metals.Suitably, the catalysts are supported catalysts. Examples of suitablesupports are alumina, silica, silica-alumina, magnesia, zirconia andmixtures of two or more of such supports. Alumina is a preferred supportmaterial, optionally in combination with silica-alumina.

Also combinations of two or more catalysts can be suitably applied.Examples of catalyst combinations include so-called stacked-bedcatalysts which comprise using different beds filled with (different)catalytic material. The choice of the specific combinations of catalystbeds will be dependent on the process mode envisaged as is known tothose skilled in the art.

An important embodiment of the process according to the presentinvention is one wherein kerosene and/or gas oil is (are) thehydroprocessed product(s) to be recovered from the process whilsthydrogen is produced in an amount exceeding the amount required tosatisfy the internal needs of the process.

The remaining hydrocracked feedstock, optionally in combination withpart, or even all of the hydroprocessed product in cases when there isno direct outlet for that product, will then be subjected to a treatmentto produce hydrogen in a single operation of which at least part isrecovered as product (in addition to the amount used to satisfy thehydrogen requirement (consumption) of the process according to thepresent invention). The surplus hydrogen can be used as export hydrogenwhich as such is then available for various applications, such aschemical reagent or as a source for producing electricity.

The process according to the invention allows for the production ofhydrogen of good quality, i.e. hydrogen having a purity of at least B0%,preferably at least 90% which enlarges the window of operation.

It will be clear that during start-up procedures, use will have to bemade of an outside hydrogen source until the process is self-sufficientwith respect to its hydrogen consumption. For instance, use can be madeof hydrogen available in storage containers.

As some hydrogen may already be present in the feedstock to thehydrogen-producing machine, it can be useful to separate it and use itas part of the amount of hydrogen needed to satisfy the hydrogenrequirement of the process. This can be conveniently done by subjectingthe hydrocracked feedstock to a separation process involving a membranewhich will allow passage of hydrogen whilst retaining heavier molecules.Those skilled in the art know which membrane to use and how to operatesuch membrane.

There are many processes known in the art which are capable of producinghydrogen from hydrocarbonaceous feedstocks. Those skilled in the artknow such processes and how to operate them. Producing hydrogen in asingle operation can be carried out in one vessel but optionally in twoor more vessels such as in a unit which is composed of a catalyticpartial oxidation step and one or more shift conversion steps. Aconvenient process is catalytic (partial) oxidation. Other suitableprocesses are steam-methane reforming and catalytic dehydrogenation oflower alkanes such as propane or butane.

A preferred hydrogen-producing system can be found in the combination ofcatalytic partial oxidation and the watergas-shift reaction which lastreaction, in essence, converts carbon monoxide, produced together withhydrogen in the catalytic partial oxidation reaction, in the presence ofwater (steam under the process conditions) to hydrogen and carbondioxide. The net result of the combined catalyticoxidation/watergas-shift reaction is that hydrocarbonaceous material isconverted into hydrogen and carbon dioxide.

Normally, the combined catalytic partial oxidation/watergas-shiftprocess can be operated at a efficiency of at least 50%, calculated onhydrogen produced, preferably with an efficiency of at least 65%,calculated on hydrogen produced (not taking into account hydrogenpresent in the hydrocracked feedstock).

Suitable catalysts for the catalytic partial oxidation process inaccordance with the process according to the present invention compriseone or more metals of Group VIII of the Periodic Table of the Elementssupported on a carrier. Examples of suitable metals comprise rhodium,iridium and ruthenium as well as combination of two or more of thesemetals. Especially carriers having a high tortuosity can be suitablyapplied. Suitable process conditions comprise using oxygen:carbon molarratios in the range between 0.30 and 0.80, preferably between 0.45 and0.75, and most preferably between 0.45 and 0.65; temperatures between800° C. and 1200° C., in particular between 900° C. and 1100° C. whilstusing a gas velocity in the range between 100,000 and 10,000,0001/kg/hr, preferably in the range between 250,000 and 2,000,000 1/kg/hr.

An advantage of the process according to the present invention is thatwhen hydrogen is produced as the main product, carbon dioxide isproduced at the same time in appreciable amounts which may be useful forcommercial operations such as for enhanced oil recovery or for heatingpurposes in the event that an appropriate infrastructure is available(such as urban communities and/or green-house agriculture).

Since feedstocks containing up to about 5% wt of sulphur can be used inthe process according to the present invention, the treatment withhydrogen will cause production of hydrogen sulphide. It will be clearthat in such instances a further process step will be necessary toremove hydrogen sulphide from the hydrocracked feedstock and to convertit into sulphur. When the pressure is released prior to separating offthe hydroprocessed product, hydrogen sulphide will be removedpreferentially and can be sent to a further processing unit such as aSCOT-unit, or, if the concentration of hydrogen is large enough it canbe fed directly to a CLAUS-unit. Those skilled in the art know suchprocessing facilities and how to operate them.

Various embodiments of the process according to the present inventioncan be schematically illustrated by means of FIGURE.

In Figure an embodiment is illustrated in which a sulphur-containingfeedstock is processed in such a way as to deliver at least onehydroprocessed product to be recovered as marketable product togetherwith hydrogen produced for use in the process according to the presentinvention as well as for export.

A feedstock is introduced via line 1 into hydrocracking unit 10 in whichthe feedstock is subjected to a catalytic treatment with hydrogen underhydrocracking conditions. Hydrogen is introduced into line 1 via line 9.From hydrocracking unit 10 the hydrocracked feedstock is sent via line 2to separating unit 20 from which a hydroprocessed product will beobtained via line 3 and a hydrogen sulphide containing hydrocrackedstream will be obtained which is sent via line 4 to a hydrogen sulphideremoval unit 30. From unit 30 a hydrogen sulphide containing stream willbe obtained which is sent via line 5 to a sulphur recovery unit (not,shown) to produce sulphur, and a hydrogen sulphide depleted hydrocrackedstream which can be sent via line 6 a to hydrogen separating unit 0.35(or in the event that hydrogen is not separated at this part in theprocess directly via line 6 (6 a+6 b) to hydrogen manufacturing unit 40)from which hydrogen separated off is sent back via line 36 to line 1 aspart of the hydrogen needed in hydrocracking unit 10 and the remaininghydrogen sulphide (and optionally hydrogen) depleted hydrocrackedfeedstock is sent via line 6 b to hydrogen manufacturing unit 40. In theevent that this unit contains a catalytic partial oxidation stage and awatergas-shift stage, water (or steam) will be sent to thewatergas-shift stage via line 11 b. Carbon dioxide will be obtained vialine 8 and: hydrogen produced will be sent back to the hydrocrackingunit 10 via lines 7 and 9 (optionally together with hydrogen via line36) whereas excess hydrogen can be made available via line 10.

In Figure a further process embodiment can be illustrated in which asulphur containing feedstock is processed in such a way that allhydrocracked feedstock (including the fraction which is recoverable ashydroprocessed product) is used to produce (excess) hydrogen, i.e. aprocess in which apart from sulphur and carbon dioxide only hydrogen isthe final product. In this embodiment the hydroprocessed productnormally to be recovered via line 3 is now sent together withhydrocracked feedstock via line 4 to hydrogen sulphide removal unit 30whereafter the further steps are as depicted in Figure.

A further embodiment in accordance with the process according to theinvention is that wherein use is made of a sulphur-free feedstock (i.e.of a feedstock of synthetic or semi-synthetic nature or of a feedstockwhich has already been subjected to a hydrodesulphurization treatment).In such embodiment, it is no longer necessary to separate off a hydrogensulphide containing hydrocracked feedstock (or to send the totalhydrocracked feedstock to the (optional) hydrogen separating unit) whichmeans that the process as schematically represented in Figure is nowoperated whithout using hydrogen sulphide removal unit 30.

EXAMPLES

The process according to the present invention can be illustrated by thefollowing prophetic examples.

Example 1

A hydrocarbonaceous feedstock having an IBP of 121° C. and a 90% boilingpoint of 533° C. and containing 0.02% by weight of sulphur can be passed(in an amount of 10 tons/day together with 1.5 tons/day of hydrogen,representative for the hydrogen/feedstock ratio) over a zeolite betatype alumina supported catalyst in hydrocracking unit 10 underconditions to convert in single pass 90% wt of the feedstock to lowerboiling material. As product, 45% wt, calculated on hydrocarbonaceousfeedstock intake, of a hydroprocessed product (comprising kerosene andgas oil) can be obtained whilst the remaining hydrocracked feedstock canbe sent to the hydrogen sulphide removal unit. After separating offhydrogen present in the hydrocracked feedstock (and returning it to thefeedstock to be used as part of the hydrogen needed in the hydrocrackingunit) after leaving the hydrogen sulphide removal unit, 55% wt,calculated on hydrocarbonaceous feedstock, can be sent to hydrogenmanufacturing unit 40 (containing a catalytic partial oxidation unit inconjunction with a watergas-shift reactor) to which steam in an amountof 7 tons/day can be added. Under the prevailing conditions, 1.1tons/day of hydrogen can be produced (together with the formation of 17tons/day of carbon dioxide). Of the amount of hydrogen produced, 200kg/day can be used to balance the hydrogen consumption in hydrocrackingunit 10 whilst 900 kg/day can be available for export.

Example 2

A hydrocarbonaceous feedstock as defined in Example 1 can be subjectedto a treatment designed at producing excess hydrogen as the main product(both in order to satisfy the internal needs of the process and forexport availability). With a hydrogen consumption of 400 kg/day andunder a conversion of 90% per pass to be obtained by using a zeolitebeta type catalyst as described in Example 1 a hydrocracked feedstock isproduced, which after hydrogen sulphide removal and separating offrecycle hydrogen can be sent in its entirety to the hydrogenmanufacturing unit which also needs to be supplied with 13.3 ton/day ofsteam. The unit can produce 2.05 ton/day of hydrogen of which an amountto satisfy the internal needs of the process can be sent to thehydrocracking unit (taking into account the amount of hydrogen alreadyliberated in the separating off operation prior to hydrogenmanufacture). Under the conditions as given above 32 ton/day of carbondioxide can be co-produced whilst 1.65 ton/day of hydrogen can becomeavailable for export.

1. Process for producing hydrogen and a hydroprocessed product from ahydrocarbonaceous feedstock, comprising subjecting the hydrocarbonaceousfeedstock to a catalytic hydrocracking treatment using hydrogen whichhas been at least partly produced from hydrocracked feedstock andsubjecting at least part of the hydrocracked feedstock, after havingsubjected it to a separation treatment in the event that hydroprocessedproduct is to be recovered, to a treatment to produce hydrogen in asingle operation which hydrogen is at least partly recovered as product,the amount, of hydrogen produced by the process exceeds the amount ofhydrogen needed in the process, wherein part or all of the non-recoveredmaterial from the catalytic hydrocracking treatment is subjected to acatalytic oxidation process which produces hydrogen and carbon(di)oxide.
 2. The process of claim 1, in which use is made of feedstocksranging from those having an initial boiling point of about ambient tothose having a final boiling point of about 650° C.
 3. The process ofclaim 2, in which use is made of feedstocks having a boiling point rangesuch that their 90% boiling point lies in the range between about 400°C. and about 600° C.
 4. The process of claim 1, in which use is made offeedstocks having a sulphur content of not more than 5% wt.
 5. Theprocess of claim 1, in which a hydrocarbonaceous feedstock is usedcontaining between about 5% wt and about 40% wt of material having aboiling point range which is the same or higher than the boiling pointrange of the hydroprocessed product to be recovered.
 6. The process ofclaim 1, in which kerosene and/or gas oil are recovered ashydro-processed products from the hydrocracked feedstock.
 7. The processof claim 1, in which the catalytic oxidation process comprises acatalytic partial oxidation step.
 8. The process of claim 1, in whichhydrogen sulphide generated by the hydrocracking treatment is convertedinto elemental sulphur by conventional means.
 9. The process of claim 1,in which use is made of a hydrocracking catalyst system capable ofconverting at least 50% wt of the material, having a boiling point rangewhich is higher than the boiling point range of the hydroprocessedproduct.
 10. The process of claim 9, in which use is made of ahydrocracking catalyst containing zeolite beta as active component. 11.The process of claim 10, in which the zeolite beta-based catalyst iscapable of converting at least 90% wt of the fraction to be treated toobtain the hydroprocessed product.
 12. The process of claim 9, in whichthe hydrocracking treatment is carried out at a temperature betweenabout 200 and about 550° C.
 13. The process of claim 9, in which thehydrocracking treatment is carried out at a pressure up to about 400atmospheres.
 14. The process of claim 9, in which the hydrocrackingtreatment is carried out at a temperature between about 250° C. andabout 450° C.
 15. The process of claim 9, in which the hydrocrackingtreatment is carried out at a pressure between about 10 and about 200atmospheres.
 16. The process of claim 1, in which the hydrogen generatedby the catalytic oxidation step has been produced at least partly fromhydrocarbons containing at most 4 carbon atoms present in thehydrocarbonaceous feedstock or as produced during the hydrocrackingtreatment.
 17. The process of claim 16, in which the feedstock to thecatalytic oxidation step consists of hydrocarbons having about 4 or lesscarbon atoms.
 18. The process of claim 1, in which hydrogen is separatedoff from the hydrocracked feedstock and from the hydroprocessed productif the latter is not to be recovered prior to the treatment to producehydrogen.
 19. The process of claim 1, in which use is made of feedstockshaving a sulphur content of below 3% wt.
 20. The process of claim 1, inwhich the catalytic oxidation process comprises a watergas-shift step.21. The process of claim 20, in which hydrogen is produced from nofeedstocks other than the hydrocarbonaceous feedstock and water used inthe watergas-shift step.
 22. The process of claim 1, in which use ismade of a hydrocracking catalyst system capable of converting at least65% wt of the material, having a boiling point range which is higherthan the boiling point range of the hydroprocessed product.